JavaScript Mutation_observer Guide
MutationObserver watches DOM changes: element insertion/removal, attribute changes, and text modifications. The guide walks through Watching Changes. `new MutationObserver(callback)`. `observer.observe(target,{childList:true,attributes:true,subtree:true})`. Records: type, target, addedNodes, removedNodes, attributeName, oldValue. Use for: detect dynamic content, script injection monitoring, non-React widget integration. The guide is organized into 1 sections that build on each other, each pairing a prose explanation with runnable code. Related guides: Arrays, Strings, Numbers, Math, Date. This is one of 145 JavaScript guides on JS Reference — see the full list on the guides page. Practice what you learn in the JavaScript playground, and look up any unfamiliar term in the JavaScript glossary.